【摘要】 对一种低合金钢的缺口试样在常温下进行了不同预加载荷的四点正、反弯曲实验,以在缺口前引入不同的微孔洞损伤量,然后通过高温回火消除残余应力和加工硬化。在-196℃低温下进行弯曲断裂实验,通过力学参数的测量和微观观察就损伤对缺口试样解理断裂韧性的影响进行了实验研究。发现,当预载荷比F0/Fgy<1.1时,预载荷对缺口解理断裂韧性基本无影响,其原因是在缺口前未产生微孔洞损伤。当F0/Fgy>1.1后,缺口解理断裂韧性随F0/Fgy的增加而迅速下降,其原因是缺口前的微孔洞损伤引起的局部高应力应变集中促使解理起裂发生在低载荷下。更多还原

【Abstract】 In this paper, a series of four point normal and reverse bending experiments with different applied loads are carried out for notched specimens of a low-alloy steel, which introduce different levels of micro-cavity damage ahead of notches. The residual stress and work hardening are removed by tempering the specimens at high temperature. Then the specimens are fractured by four point bending at a low temperature of -196℃. By measurement of mechanical parameter and microscopic observation, the effects of damage on the cleavage fracture toughness of notched specimens are experimentally investigated. It has been found that when the pre-load ratio F 0/ F gy is less than 1.1, it has essentially no effect on the cleavage fracture toughness of the notched specimens. The reason for this is that no micro-cavity damage is introduced ahead of notches. After the F 0/ F gy is larger than 1.1, the cleavage fracture toughness decreases rapidly with increasing the F 0/ F gy . The reason for this is that the local high stress and strain induced by the micro-cavities ahead of notches promote the cleavage initiating at low applied loads.更多还原